Well, considering you are telling the truth:

a) you never trained your IQ using methods designed to increase IQ, meaning your self-assessed avg IQ would increase significantly within 150 hours of IQ practice

b) 1 cigarette is irrelevant, which makes c) irrelevant in context.

d) It's common to feel smarter than the rest. Especially if you surround yourself with people who tend to keep their intelligence back for the sake of recreation and fun OR they never really tried for reasons.

Chess is cool, ELO 1350 - 1450 after 3 years of regular playing is also cool and shows that chess is something where you actually are trying, pointing at the fact that your self-confidence issues are merely the result of lack of practice aka consistent increases of mastery in subjects you care for (or want to care for).

Bottom line: You (most likely, > 0.97) did not lose any IQ points due to smoking. :D